DISEASE CHARACTERISTICS: Histologically or cytologically confirmed metastatic small cell lung cancer (SCLC) Must have sensitive or refractory disease after first-line chemotherapy Refractory Progressive or stable disease during chemotherapy Relapse after a response during treatment Relapse after a response within 3 months after completing chemotherapy Sensitive Relapse after a response of at least 3 months duration after completing chemotherapy At least 1 measurable lesion No previously irradiated lesions No symptomatic brain or leptomeningeal metastasis